For smokers who think they're buying insurance against lung cancer by taking vitamins, a new study finds they may want to rethink that choice.

According to researchers at the University of Washington in Seattle who surveyed 77,000 vitamin users, vitamins do not protect against lung cancer. In fact, certain ones can raise the risk.

The higher the dose of vitamin E per day, the higher the risk of developing lung cancer, suggests the study, published in the first March issue of the American Thoracic Society's American Journal of Respiratory and Critical Care Medicine.

"Indeed, increasing intake of supplemental vitamin E was associated with a slightly increased risk of lung cancer," said study author Christopher Slatore in a release.

Researchers found that for every additional 100mg/day of vitamin E, the risk of lung cancer went up seven per cent. Over a 10-year period, that risk would translate into a 28 per cent increased risk.

Vitamin E supplementation was most likely to increase the risk of small cell lung cancer, the study found. Current smokers were found to be most at risk.

"Patients should be counselled against using these supplements to prevent lung cancer," according to the study.

It examined the vitamin consumption habits of 77,126 men and women who were between 50 and 76 years old and lived in Washington state.

Researchers predicted their risk of lung cancer in the four years following their enrolment in the study, taking into account their smoking status, vitamin usage and other factors.

The study was carried out between October 2000 and December 2006.

Of the group, 521 developed lung cancer, a finding that was in line with researchers' expectations.

As for the other vitamins studied, such as multivitamins, vitamin C, and folate, they did "not show any evidence for a decreased risk of lung cancer," said Slatore.

The authors point out that eating fruit and vegetables as a way of staving off cancer has more benefit, as they contain vitamins and phytochemicals that play a more complex — and not fully understood — role in cancer prevention.